Process for manufacturing a semiconductor device comprising a metal-compound film

ABSTRACT

There is provided a semiconductor device comprising a dielectric film made of a high dielectric constant material, in which a leak current is reduced in the film and which exhibits improved device reliability. Specifically, a dielectric film  142  is a metal-compound film having a composition represented by the formula MO x C y N z  wherein x, y and z meet the conditions: 0&lt;x, 0.1≦y≦1.25, 0.01≦z and x+y+z=2; and M comprises at least Hf or Zr.

This application is a division of co-pending application Ser. No.10/807,248, filed on Mar. 24, 2004, the entire contents of which arehereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a semiconductor device comprising ametal-compound film on a semiconductor substrate and a manufacturingprocess therefore.

BACKGROUND OF THE INVENTION

A high dielectric constant (so-called “high-k”) film has been recentlyinvestigated as a component in a semiconductor device. Representativeexamples of a high-k material include Zr- and Hf-containing oxides. Sucha material can be used for a dielectric film in a capacitor or a gateinsulating film in an MOSFET to achieve good device performance whichhas not been obtained by the prior art.

Japanese patent application NO. 2002-373945 discloses a capacitorcomprising such a high-k material. Therein, a dielectric film made ofthe high-k material is formed by atomic layer deposition (ALD). The ALDprocess in which one-atomic layers are deposited one by one hasadvantages that a deposition process may be conducted at a lowertemperature and that a film with good film properties may be obtained.

FIG. 2 shows a cross-sectional view of the capacitor described inJapanese patent application NO. 2002-373945. Therein, on a substrate 21are formed a device separating region 22 while in a device region isformed a transistor consisting of a gate electrode 23 and a source/draindiffusion layer 24. On both sides of the gate electrode 23, there areformed side walls 25. An unshown cobalt silicide film covers over thegate electrode 23 and the source/drain diffusion layer 24.

On the transistor is formed a bit line 29 via a cell contact 28. On thetransistor is formed a cylindrical MIM capacitor via a capacitor contact31. The capacitor has a structure that there are laminated a lowerelectrode 34, a dielectric film 35 and an upper electrode 36 aredeposited, on which a tungsten film 37 is formed. An insulating film forthe dielectric film 35 is made of a metal material such as ZrO₂. Thedielectric film 35 is deposited by atomic layer deposition.

When forming a ZrO₂ film by atomic layer deposition, deposition gas usedgenerally comprises ZrCl₄ and H₂O. The above reference has alsodescribed that a ZrO₂ layer can be formed by the method. There havebeen, however, increased needs for a high-k film with much higher filmproperties and for a deposition process with a higher productionefficiency. Any deposition process according to the prior art cannotadequately meet the needs. Furthermore, it has been strongly needed thata leak current is reduced in a capacitor comprising a high-k material.

Furthermore, there have been attempts to use a high-k material for agate insulating film in a transistor. Using such a material, a film canbe thin as calculated as a silicon oxide film even when making a gateinsulating film thicker to some extent, so that a physically andstructurally stable gate insulating film can be achieved. However, in atransistor comprising such a gate insulating film, dopants introduced ina gate electrode may sometimes penetrate the gate insulating film toreach a channel region. Dopant penetration may significantly deterioratereliability of a semiconductor device without transistor properties asdesigned. In designing a transistor comprising a high-k gate insulatingfilm, adequately preventing such dopant penetration is an importanttechnical problem.

In view of the above situation, an objective of this invention is togive a semiconductor device comprising a film made of a high dielectricconstant material with a reduced leak current in the film and withimproved device reliability.

Another objective of this invention is to provide a capacitor with ahigher capacity and a reduced leak current.

A further objective of this invention is to provide a transistorcomprising a gate insulating film with a smaller thickness as calculatedas a silicon oxide film and with improved reliability.

SUMMARY OF THE INVENTION

This invention provides a semiconductor device comprising asemiconductor substrate and a metal-compound film thereon, wherein themetal-compound film has a composition represented by the formula:MO_(x)C_(y)N_(z)

wherein x, y and z meet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z andx+y+z=2; and M comprises at least Hf or Zr.

This invention also provides a semiconductor device comprising asemiconductor substrate, a pair of electrodes thereon and a capacitorcomprising a dielectric film between the electrodes, wherein thedielectric film comprises a metal-compound film having a compositionrepresented by the formula:MO_(x)C_(y)N_(z)

wherein x, y and z meet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z andx+y+z=2; and M comprises at least Hf or Zr.

The semiconductor device may further comprise a gate electrode formed onthe semiconductor substrate; a transistor comprising a source and adrain regions formed in the semiconductor substrate whose surfaces aresilicided; and a connecting plug for connecting the source and the drainregions in the transistor with the capacitor.

This invention also provides a semiconductor device comprising asemiconductor substrate; a gate insulating film formed on the mainsurface of the semiconductor substrate; a gate-electrode on the gateinsulating film; and a source and a drain regions formed on thesemiconductor substrate which together sandwich the gate electrode,wherein the gate insulating film comprises a metal-compound film havinga composition represented by the formula:MO_(x)C_(y)N_(z)

wherein x, y and z meet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z andx+y+z=2; and M comprises at least Hf or Zr.

This invention also provides a process for manufacturing a semiconductordevice, comprising the step of forming a metal-compound film having acomposition represented by the formula:MO_(x)C_(y)N_(z)

wherein x, y and z meet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z andx+y+z=2; and M comprises at least Hf or Zr, on a semiconductor substrateby atomic layer deposition.

This invention also provides a process for manufacturing a semiconductordevice comprising forming a first electrode, a dielectric film and asecond electrode on a semiconductor substrate, wherein the step offorming the dielectric film comprises forming a metal-compound filmhaving a composition represented by the formula:MO_(x)C_(y)N_(z)

wherein x, y and z meet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z andx+y+z=2; and M comprises at least Hf or Zr, on a semiconductor substrateby atomic layer deposition.

The process for manufacturing a semiconductor device may furthercomprise the steps of forming a gate electrode on the semiconductorsubstrate; introducing a dopant into the main surface of thesemiconductor substrate to form a source and a drain regions such thatthe gate electrode is sandwiched between the regions; siliciding thesurfaces of the source and the drain regions; and forming an interlayerinsulating film over the gate electrode, the source region and the drainregion, then selectively removing the interlayer insulating film to forma contact hole reaching the source and the drain regions, and thenfilling the contact hole with a metal film to form a connecting plug,wherein the first electrode is formed such that the connecting plug isconnected with the first electrode; the dielectric film is formed at200° C. to 400° C. both inclusive; and the first and the secondelectrodes are formed at 500° C. or lower.

This invention also provides a process for manufacturing a semiconductordevice comprising the steps of forming a gate insulating film on asemiconductor substrate; forming a gate electrode film on the gateinsulating film; shaping the gate insulating film and the gate electrodefilm into a given shape to form a gate electrode; and introducing adopant into the main surface of the semiconductor substrate to form asource and a drain regions such that the gate electrode is sandwichedbetween the regions, wherein the step of forming the gate insulatingfilm comprises forming a metal-compound film having a compositionrepresented by the formula:MO_(x)C_(y)N_(z)

wherein x, y and z meet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z andx+y+z=2; and M comprises at least Hf or Zr, on a semiconductor substrateby atomic layer deposition.

A semiconductor device according to this invention comprises ametal-compound film represented by the above formula MO_(x)C_(y)N_(z).The metal-compound film comprises carbon and nitrogen within aparticular composition range, so that a leak current can besignificantly reduced. By our study, it has been confirmed that flatnessin a film surface can be improved by using a metal-compound film havingthe above particular composition. It would thus contribute to reductionin a leak current between the metal-compound film and the adjacent film.Although the reason why flatness in the surface of the metal-compoundfilm is improved is not clearly understood, it would be speculated thata film composition in which carbon and nitrogen are contained within aparticular range may lead to reduction in a size of grains constitutingthe film, resulting in improved flatness in the film surface.

Reduction in a leak current may be more significant when applying thisinvention to a capacitor. A capacitor has a configuration where adielectric film made of a dielectric is disposed between a pair of metalelectrodes, so that a leak current tends to generate in an interfacebetween the different materials. According to this invention, surfaceflatness in a dielectric film comprising the above metal-compound filmcan be improved, so that a leak current in such an interface may beeffectively reduced.

Furthermore, when applying this invention to a transistor, migration ofdopants within a gate insulating film can be inhibited and dopantpenetration described in “Description of the Prior Art” can beinhibited. Although the reason is not clearly understood, it would bespeculated that a film composition containing carbon and nitrogen withina particular range may lead to reduction in a size of grainsconstituting the film, so that migration of the dopants via a grainboundary.

A process for manufacturing a semiconductor device according to thisinvention employing chemical vapor deposition, preferably atomic layerdeposition may consistently provide a semiconductor device having theabove good properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structure of a capacitor according to an embodiment.

FIG. 2 shows a structure of a capacitor according to the prior art.

FIG. 3A and FIG. 3B illustrate a process for manufacturing a capacitoraccording to an embodiment.

FIG. 4C and FIG. 4D illustrate a process for manufacturing a capacitoraccording to an embodiment.

FIG. 5E and FIG. 5F illustrate a process for manufacturing a capacitoraccording to an embodiment.

FIG. 6G and FIG. 6H illustrate a process for manufacturing a capacitoraccording to an embodiment.

FIG. 7I and FIG. 7J illustrate a process for manufacturing a capacitoraccording to an embodiment.

FIG. 8A and FIG. 8B show exemplary sequences for depositing an oxidefilm and an oxynitride film, respectively.

FIG. 9 is a conceptual diagram of a remote plasma.

FIG. 10 shows a structure of a decoupling capacitor according to anembodiment.

FIG. 11 shows a structure of a transistor according to an embodiment.

FIG. 12A, FIG. 12B, FIG. 12C and FIG. 12D illustrate a process formanufacturing a transistor according to an embodiment.

FIG. 13E and FIG. 13F illustrate a process for manufacturing atransistor according to an embodiment.

FIG. 14 shows properties of the capacitors evaluated in Examples.

DETAILED DESCRIPTION OF THE INVENTION

In this invention, the formula MO_(x)C_(y)N_(z) may meet the conditions:0.7≦x≦1.85 and 0.05≦z≦0.2 to more reliably reduce a leak current in themetal-compound film. Furthermore, 0.1 or less of z indicating a nitrogenratio may increase a relative oxygen ratio to improve a dielectricconstant. The metal-compound film defined by the above formulaMO_(x)C_(y)N_(z) may contain additional trace elements.

A semiconductor device of this invention may further comprise a gateelectrode formed on a semiconductor substrate; a transistor comprising asource and a drain regions formed in the semiconductor substrate whosesurfaces are silicided; and a connecting plug for connecting the sourceand the drain regions in the transistor with the capacitor. Silicidingthe surfaces of the source and the drain regions may reduce a resistancein the source and the drain regions and reduce a contact resistance ofthe connecting plug with the source and the drain regions, resulting inhigher-speed transistor operation.

When forming the metal-compound film by atomic layer deposition in thisinvention, the deposition gas may comprise:M(NRR′)₄

wherein M comprises at least Hf or Zr; and R and R′ independentlyrepresent hydrocarbon, so that the metal-compound film having the aboveparticular composition may be consistently provided and contaminationwith particles derived from the deposition gas may be inhibited,resulting in more improved metal-compound film properties.

In this invention, after forming the metal-compound film, the film maybe annealed in nitrogen or a nitrogen-containing gas, to introducenitrogen into the film. Such introduction of nitrogen into themetal-compound film can further reduce a leak current.

When applying this invention to a capacitor, the following configurationmay be employed. The device may further comprise a gate electrode formedon a semiconductor substrate; a transistor comprising a source and adrain regions formed in the semiconductor substrate whose surfaces aresilicided; and a connecting plug for connecting the source and the drainregions in the transistor with the capacitor. Siliciding the surfaces ofthe source and the drain regions may reduce a resistance in the sourceand the drain regions and reduce a contact resistance of the connectingplug with the source and the drain regions, resulting in higher-speedtransistor operation. In such a silicided source or drain region,silicide aggregation may be caused in a process at an elevatedtemperature of, for example, 500° C. or higher. For the capacitoraccording to this invention, a dielectric film can be formed by alow-temperature deposition process at 200° C. to 400° C. such as atomiclayer deposition, so that such aggregation can be prevented. Asemiconductor device having such a configuration may be manufactured bythe steps of forming a gate electrode on the semiconductor substrate;introducing a dopant into the main surface of the semiconductorsubstrate to form a source and a drain regions such that the gateelectrode is sandwiched between the regions; siliciding the surfaces ofthe source and the drain regions; and forming an interlayer insulatingfilm over the gate electrode, the source region and the drain region,then selectively removing the interlayer insulating film to form acontact hole reaching the source and the drain regions, and then fillingthe contact hole with a metal film to form a connecting plug. In theprocess, the first electrode is formed such that the connecting plug isconnected with the first electrode. In addition, the first and thesecond electrodes are formed at 500° C. or lower. A lower limit for thetemperature may be appropriately selected depending on a depositionmethod; for example, 100° C. or higher.

The step of siliciding the surfaces of the source and the drain regionsmay comprise forming a metal film made of a transition metal adjacent tothe source and the drain regions and then heating the film. Examples ofa transition-metal film may include cobalt and nickel films. Whenemploying such a configuration, the step of forming the first electrode,the dielectric film and the second electrode in the capacitor must beconducted at 500° C. or lower. At a temperature higher than 500° C.,silicide formed in the source and the drain regions may be aggregated,leading to an increased contact resistance of the connecting plug withthe source and the drain regions. For forming an electrode and adielectric film by a low-temperature process, it is preferable that anelectrode material is properly selected and the dielectric film isdeposited by atomic layer deposition. Given these conditions, preferableexamples of an electrode material include materials containing Ti, W,Pt, Ir, Ru or a nitride thereof.

Preferred embodiments of this invention will be described with referenceto the drawings.

Embodiment 1

This embodiment relates to a cylinder type MIM capacitor. FIG. 1schematically shows a structure of the capacitor according to thisembodiment, which a cylinder type MIM capacitor is formed, via acapacitor contact 131, on a transistor comprising a gate electrode 123and a source-drain region 124. The capacitor has a structure in which alower electrode (a first electrode) 140, a dielectric film 142, an upperelectrode (a second electrode) 144 and a tungsten film are sequentiallydeposited and these are patterned. A bit line 129 is formed on thetransistor via a cell contact 128. Although the bit line 129 and thecapacitor contact 131 are drawn in the same cross-sectional view in FIG.1, it is for the sake of deeper understanding of the whole structure,but actually these are not crossed. In this configuration, there isdisposed a bit line 129 in a gap in the region where the capacitorcontact 131 is disposed.

The dielectric film 142 is a metal-compound film having a compositionrepresented by ZrO_(x)C_(y)N_(z) wherein x, y and z meet the conditions:0<x, 0.1≦y≦1.25, 0.01≦z, x+y+z=2. A metal-compound film having such acomposition cannot be obtained simply by selecting a deposition gas asappropriate, but can be obtained only by appropriately selecting adeposition gas and optimizing the deposition conditions.

Since a dielectric film is made of a metal compound having such aparticular composition, a capacitor according to this embodiment has ahigh capacity while a leak current is significantly reduced. There willbe described the process for manufacturing a device shown in FIG. 1.

First, a transistor is formed as shown in FIG. 3A. On a siliconsubstrate 121 are formed a device separating region 122 and then a gateelectrode 123 via an unshown gate insulating film. Then, a dopant ision-implanted around the surface of the substrate 121 to form asource-drain region 124. Then, on the surfaces of the gate electrode 123and the source-drain region 124 is formed a cobalt film, which is heatedto form a cobalt silicide film. On the transistor thus formed is formedan interlayer insulating film 126.

Next, the interlayer insulating film 126 is selectively dry-etched toform a contact hole reaching the source-drain region 124. Then, on thecontact hole are formed TiN/Ti as a barrier film and then a tungstenfilm such that the hole is filled with the latter. The tungsten was thenpolished by CMP to form a tungsten plug. Thus, cell contacts 127, 128are formed as shown in FIG. 3B.

Then, on the cell contacts 127, 128 are sequentially formed a bit line129 and an interlayer insulating film 130. The upper surface of theinterlayer insulating film 130 is leveled by CMP (chemical mechanicalpolishing) (FIG. 4C).

Next, the interlayer insulating film 130 is dry-etched to form a contacthole reaching the cell contact 127. A tungsten film was deposited tofill the contact hole and CMP was conducted to form a capacitor contact131 (FIG. 4D). Although the bit line 129 and the capacitor contact 131are drawn in the same cross-sectional view in FIG. 4D, it is for thesake of deeper understanding of the whole structure, but actually theseare not crossed.

Then, as shown in FIG. 5E, on the capacitor contact 131 is formed aninterlayer insulating film 132. Then, as shown in FIG. 5F, in theinterlayer insulating film 132 is opened a cylinder 133 for forming acapacitor. The cylinder 133 may have, for example, an ellipticalcylindrical shape with a depth of 300 to 500 nm, a longer axis of 0.3 to0.5 μm and a shorter axis of 0.15 to 0.3 μm.

Then, as shown in FIG. 6G, a lower electrode 140 is formed by CVD to afilm thickness of 5 to 40 nm.

The inside of the cylinder 133 is filled with a photoresist, the wholesurface of the substrate is etched back, and then the photoresist in theinside of the cylinder 133 is removed by oxygen plasma processing andorganic stripping. Thus, the lower electrode 140 on the outside of thecylinder 133 is removed (FIG. 6H).

Then, over the whole surface of the substrate are sequentially depositeda dielectric film 142 and an upper electrode 144. Herein, the dielectricfilm 142 is formed by atomic layer deposition (ALD).

The dielectric film 142 has a composition represented byZrO_(x)C_(y)N_(z) wherein x, y and z meet the following conditions: 0<x,0.1≦y≦1.25, 0.01≦z, x+y+z=2.

Among deposition gas components used in deposition of the dielectricfilm 142, a metal source gas is a metal compound represented by thegeneral formula Zr(NRR′)₄ wherein R and R′ independently representhydrocarbon, preferably straight or branched alkyl. As R or R′,preferred is alkyl having up to 6 carbon atoms; for example, methyl,ethyl, propyl and tert-butyl.

Preferable examples of the above source gas include Zr(N(C₂H₅)₂)₄,Zr(N(CH₃)₂)₄ and Zr(N(CH₃)(C₂H₅))₄. Such a compound may be selected toobtain a film with a flat surface and to prevent particles fromcontaminating the film, resulting in a dielectric film with a reducedleak current and good film properties.

An oxidizer gas used in deposition of the dielectric film may be oxygenor an oxygen-containing compound such as NO, NO₂, N₂O, H₂O, O₂ and O₃.Among these, NO, NO₂ and N₂O are preferable, and a combination of anitriding and an oxidizing gases such as a mixture of NO and NO₂ or NOand O₃ is more preferable. Such a gas may be selected to consistentlyobtain a dielectric film with good film properties. While H₂O tends toremain in a deposition system in a process employing H₂O as an oxidizingagent frequently used in the prior art, NO, N₂O or NO₂ may be easilyremoved from a deposition system by purging, resulting in an improvedproduction efficiency.

For example, a ZrO₂ film was deposited to 10 nm by one of the followingmethods. A required deposition time was 20 min and 18 min in Methods 1and 2, respectively, while being 55 min in Method 3.

Method 1

Deposition gas: Zr(N(CH₃)(C₂H₅))₄+NO

Method 2

Deposition gas: Zr(N(CH₃)(C₂H₅))₄+O₃

Method 3

Deposition gas: ZrCl₄+H₂O

A deposition temperature for the dielectric film 142 is preferably 200°C. to 400° C. both inclusive. At a temperature lower than 200° C.,impurities in the ZrO₂ film may increase. At a temperature higher than400° C., decomposition of Zr(NRR′)₄ may be initiated on a substrate onwhich deposition occurs to cause contamination with impurities to anunacceptable level. At an excessively higher deposition temperature, acrystal grain size may be increased, leading to an increased leakcurrent.

A ratio of a metal-containing deposition gas to an oxidizing gas (ametal-containing deposition gas/an oxidizing gas) is preferably 1/100 orless for reducing impurities in the film.

When using a mixture of NO and N₂ as an oxidizing gas, a ratio of NO/N₂is preferably 1/10,000 or more.

A pressure during deposition is, for example, 10 mtorr to 10 torr.

A deposition gas may be fed, for example, as shown in FIG. 8A and FIG.8B. FIG. 8A and FIG. 8B show exemplary sequences for depositing an oxidefilm and an oxynitride film, respectively. In FIG. 8B, ammonia isintroduced during deposition to form an oxynitride film. In the figure,a “deposition gas” indicates a metal-compound source gas and an“oxidizing agent” indicates oxygen or an oxygen-containing compound gas.There will be described the sequence in FIG. 8A for the case where adeposition gas, an oxidizer gas and a purge gas are Zr (N(CH₃)(C₂H₅))₄,NO and an inert gas, respectively.

First, by feeding Zr (N(CH₃)(C₂H₅))₄ as a source material into a chamberin an ALD apparatus, a reaction is initiated in the lower electrodesurface to grow only one atomic layer. After stopping feeding of Zr(N(CH₃)(C₂H₅))₄, an inert gas, typically Ar or N₂ is fed as a purge gasinto the chamber to remove excessive unreacted Zr(N(CH₃)(C₂H₅))₄.

Then, NO is fed to remove a functional group having a Zr terminus whichhas grown on the substrate. After stopping feeding of NO, an inert gas,typically Ar or N₂ is fed as a purge gas to remove unreacted NO andreaction byproducts. Then, the purge gas is stopped.

The sequential cycle of Zr (N(CH₃)(C₂H₅))₄ feeding, purging, NO feedingand purging can be repeated a desired number of times to give adielectric film 142 made of ZrO_(x)C_(y)N_(z) wherein x, y and z meetthe conditions: 0<x, 0.1≦y≦1.25, 0.01≦z, x+y+z=2, having a thickness of5 to 15 nm.

In addition to appropriately selecting a deposition gas, it is alsoimportant to select the optimum deposition conditions depending on thedeposition gas for allowing x, y and z in ZrO_(x)C_(y)N_(z) to meet theconditions: 0<x, 0.1≦y≦1.25, 0.01≦z and x+y+z=2. The deposition gas ispreferably the above metal compound represented by Zr(NRR′)₄ wherein Rand R′ independently represent straight or branched alkyl. In terms ofthe deposition conditions, a deposition temperature, a depositionpressure, a deposition rate and a deposition gas are selected asappropriate.

After forming the dielectric film 142, an upper electrode 144 is formedby CVD to a thickness of 5 to 40 nm. Now, the state shown in FIG. 7I isobtained.

Then, as shown in FIG. 7J, a tungsten film 146 is formed such that theinside of the cylinder 133 is filled. On the tungsten film is formed aresist film having a given opening, which is then used as a mask forselective dry etching of the tungsten film 146 to separate devices.Thus, an MIM type capacitor as shown in FIG. 1 is provided.

The MIM type capacitor thus formed is a high capacity device because itcomprises a dielectric film made of ZrOCN which is a highly insulatingmaterial with a higher dielectric constant. Furthermore, sinceinterfaces between the lower electrode and the dielectric film andbetween the dielectric film and the upper electrode can be stably keptin a good state, reduction in a capacitance value and increase indielectric film leak can be effectively prevented.

There has been described an example of a cylinder type capacitor, butthis invention is not limited to it. Thus, this invention may be appliedto a planar or box type capacitor.

Embodiment 2

In Embodiment 1, after forming the dielectric film 142, the dielectricfilm 142 may be nitrided by a plasma using a nitrogen-containingcompound such as N₂O and NH₃, to more effectively reduce a leak currentin a capacitor.

In such a nitriding process, it is preferable to use a remote plasma.FIG. 9 is a conceptual diagram of a remote plasma. A plasma is generatedin a plasma generation chamber equipped with a gas inlet, a wave guideand microwave application means, which is placed separately from adeposition chamber where a substrate is disposed. The plasma generatedis introduced via a quartz tube into the chamber in which the substrateis disposed. In the chamber, the surface of the substrate is subjectedto plasma processing. In FIG. 9, nitrogen alone is introduced forgenerating a plasma. Such a procedure may be employed to adequatelyconduct nitriding while preventing the substrate from being damaged. Thefollowing plasma conditions may be selected.

Temperature: 400 to 450° C.;

Plasma power: 400 W to 5,000 W;

Flow rate of N₂ or NH₃: 0.5 L to 5 L/min;

Pressure: 1 mtorr to 10 torr.

Embodiment 3

This embodiment is an example where this invention is applied to adecoupling capacitor. A decoupling capacitor is a high dielectricconstant film capacitor formed over an interconnect in an LSI forcompensating a voltage reduction induced by a parasitic inductancebetween a power source and the LSI interconnect. In this embodiment, adielectric film in the capacitor is formed by ALD whereby the dielectricfilm can be deposited at a lower temperature and which can eliminate theneed for post-annealing under an oxidizing atmosphere, allowing the MIMtype film capacitor to act as a decoupling capacitor between powersources.

FIG. 10 is a partial cross-sectional view of a semiconductor deviceaccording to this embodiment. On an uppermost interconnect (groundingwire) 201 and an uppermost interconnect (power wire) 202 is formed aninterlayer film 205, on which are sequentially formed a lower electrode206, a dielectric film 207 and an upper electrode 208, to provide adecoupling capacitor 210. The lower electrode 206 and the uppermostinterconnect (grounding wire) 201 are connected via a contact plug 203,while the upper electrode 208 and the uppermost interconnect (powerwire) 202 are connected via a contact 204.

There will be described a process for manufacturing a decouplingcapacitor shown in FIG. 10. First, an interlayer film 205 is depositedon uppermost interconnects 201, 202 in a logic device prepared accordingto a well-known manufacturing process. In the interlayer film 205 isformed a contact hole, which is then filled by depositing one or two ormore of the materials selected from the group consisting of Cu, Al, TiNand W. Then, CMP is conducted to form contact plugs 203, 204. After CMP,on the interlayer film 205 and the contact plugs 203, 204 is deposited alower electrode film made of at least one material selected from thegroup consisting of TiN, Ti, TaN, Ta, W, WN, Pt, Ir and Ru by reactivesputtering or ALD. The lower electrode film is shaped into apredetermined shape to form a lower electrode 206.

After forming the lower electrode 206, a dielectric film is formed byALD at a deposition temperature of 200 to 400° C. The dielectric filmhas a composition represented by ZrO_(x)C_(y)N_(z) wherein x, y and zmeet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z and x+y+z=2. A filmthickness is about 2 to 15 nm. The procedure for depositing the film anda deposition and an oxidizer gases used are as described inEmbodiment 1. Since a metal-compound film having such a particularcomposition is used as a dielectric film, this embodiment can provide acapacitor with a higher capacity and a reduced leak current.

After shaping the dielectric film into a desired shape to obtain adielectric film 207, on which is deposited an upper electrode film madeof at least one material selected from the group consisting of TiN, Ti,TaN, Ta, W, WN, Pt, Ir and Ru by sputtering or ALD. It is then shapedinto a desired shape to form an upper electrode 208 to give a filmcapacitor within the semiconductor device, which acts as a decouplingcapacitor.

Although the lower electrode is connected to the uppermost interconnect(grounding wire) while the upper electrode is connected to the uppermostinterconnect (power wire) in FIG. 10, this invention is not limited tothe configuration. A configuration with a different connection stylewhere the lower electrode is connected to the uppermost interconnect(power wire) while the upper electrode is connected to the uppermostinterconnect (grounding wire), may be, of course, similarly effective.

Although the film capacitor acting as a decoupling capacitor is formedright above the uppermost interconnect in the device in FIG. 10, thecapacitor is not necessarily to be above the uppermost interconnect, butmay be formed in any of the inside and the lower part of the device.

As described above, according to Embodiment 3, a dielectric film havinga high dielectric constant can be formed by ALD allowing deposition at alower temperature and eliminating the need for post-annealing under anoxidizing atmosphere, to form a film capacitor within a semiconductordevice without property deterioration or yield reduction due tooxidation of an interconnect layer.

The film capacitor may be used as a decoupling capacitor to solve theproblems in a conventional on-chip decoupling capacitor while achievingadvantages in an on-chip decoupling capacitor, i.e., a low inductanceand a high capacity.

A film capacitor comprising a dielectric film having the aboveparticular composition can be formed on the uppermost interconnect in asemiconductor device to achieve an on-chip decoupling capacitor with alower inductance and a higher capacity, which can adequately deal withspeeding-up in an LSI.

Embodiment 4

In this embodiment, this invention is applied to an MOSFET. An MOSFETaccording to this embodiment has a structure shown in FIG. 11. Atransistor in FIG. 11 comprises a gate electrode consisting of a gateinsulating film consisting of a laminate of a silicon oxynitride film402 and a metal-compound film 404 on a silicon substrate 400 and a gateelectrode 406 made of polysilicon. On the lateral face of the gateelectrode is formed a side wall 410 comprised of a silicon oxide film.On the surface of the silicon substrate 400 adjacent to both sides ofthe gate electrode is formed a source-drain region 412 in which a dopantis dispersed.

The metal-compound film 404 has a composition represented byHfO_(x)C_(y)N_(z) wherein x, y and z meet the conditions: 0<x,0.1≦y≦1.25, 0.01≦z and x+y+z=2. Such a film can be used to effectivelyprevent a dopant in the gate electrode from penetrating into the siliconsubstrate.

Preferable examples of a source gas for depositing the abovemetal-compound film include Hf(N(C₂H₅)₂)₄, Hf(N(CH₃)₂)₄ andHf(N(CH₃)(C₂H₅))₄. Such a compound can be selected to more effectivelyprevent a dopant in the gate electrode from penetrating into the siliconsubstrate.

There will be described a process for manufacturing a transistor shownin FIG. 11 with reference to FIG. 12A, FIG. 12B, FIG. 12C, FIG. 12D,FIG. 13E and FIG. 13F. First, a silicon substrate 400 whose surface hasbeen washed with a given chemical is prepared as shown in FIG. 12A.Then, as shown in FIG. 12B, a silicon oxynitride film 402 is depositedby CVD on the main surface of the silicon substrate 400. Then, as shownin FIG. 12C, a metal-compound film 404 is formed by atomic layerdeposition. A metal source gas in a deposition gas used in thedeposition is a metal compound represented by the general formula:Hf(NRR′)₄

wherein R and R′ independently represent hydrocarbon, preferablystraight or branched alkyl. R and R′ are preferably alkyl having up to 6carbon atoms; for example, methyl, ethyl, propyl and tert-butyl.

An oxidizer gas used in deposition of the metal-compound film 404 may beoxygen or an oxygen-containing compound such as NO, NO₂, N₂O, H₂O, O₂and O₃. Among these, NO, NO₂ and N₂O are preferable, and a combinationof a nitriding and an oxidizing gases such as a mixture of NO and NO₂ orNO and O₃ is more preferable. Such a gas may be selected to consistentlyobtain a dielectric film with good film properties. NO, N₂O or NO₂ maybe easily removed from a deposition system by purging, resulting in animproved production efficiency.

A deposition gas may be fed as described below. First, by feeding Hf(N(CH₃)(C₂H₅))₄ as a source material into a chamber in an ALD apparatus,a reaction is initiated in the lower electrode surface to grow only oneatomic layer. After stopping feeding of Hf(N(CH₃)(C₂H₅))₄, an inert gas,typically Ar or N₂ is fed as a purge gas into the chamber to removeexcessive unreacted Hf (N(CH₃)(C₂H₅))₄.

Then, NO is fed to remove a functional group having a Hf terminus whichhas grown on the substrate. After stopping feeding of NO, an inert gas,typically Ar or N₂ is fed as a purge gas to remove unreacted NO andreaction byproducts. Then, the purge gas is stopped.

The sequential cycle of Hf(N(CH₃)(C₂H₅))₄ feeding, purging, NO feedingand purging is repeated a desired number of times to give ametal-compound film 404 made of HfO_(x)C_(y)N_(z) wherein x, y and zmeet the conditions: 0<x, 0.1≦y≦1.25, 0.01≦z, x+y+z=2, having athickness of 5 to 15 nm.

Then, as shown in FIG. 12D, on the metal-compound film 404 is formed agate electrode film 406. The gate electrode film 406 may be preferablymade of polycrystal, but may be another type of metal electrode such asSiGe, TiN, WN and Ni.

Next, as shown in FIG. 13E, the silicon nitride film 402, themetal-compound film 404 and the gate electrode film 406 are etched intogiven shapes to obtain a gate electrode. Then, while forming a side wall410 on the lateral face of the gate electrode, a dopant is introducedinto the gate electrode and the surface of the silicon substrate 400adjacent to both sides of the gate electrode. Thus, an MOSFET shown inFIG. 13F is prepared.

In the MOSFET according to this embodiment, since the gate insulatingfilm comprises a metal-compound film 404 having the above particularcomposition, it can effectively prevent a dopant in the gate electrodefilm 406 from penetrating the gate insulating film into the siliconsubstrate 400. Thus, a highly reliable transistor can be obtained.

Although there have been described preferred embodiments of thisinvention, it will be apparent to those skilled in the art that theseembodiments are only illustrative and that there may be many variations,which can be encompassed within this invention.

For example, a Zr-containing and an Hf-containing films are used for acapacitor and a transistor, respectively, in the above embodiments. AnHf-containing and a Zr-containing films may be, on the contrary, usedfor a capacitor and a transistor, respectively. A film containing bothHf and Zr may be used as a capacitive and/or a gate insulating films.

A capacitive or gate insulating film may be single-layered ormulti-layered. When being multi-layered, it may comprise a plurality ofmetal-compound films having the above particular composition. In amultilayered structure, the individual layers may have differentcompositions, for example, as in a laminate film of ZrOCN and HfOCN aslong as they have a composition within the above particular range.

In a capacitive or gate insulating film, a part in contact with anelectrode may be made of a material other than that in the abovemetal-compound film. For example, in an interface between a gateinsulating film and a silicon substrate or an interface between a gateinsulating film and a gate electrode, a metal nitride or metaloxynitride film may be formed for preventing a reaction of silicon withthe metal-compound film.

EXAMPLES

On a silicon substrate was formed a transistor. In the upper part of thetransistor was formed a cylindrical type capacitor having the structurein FIG. 1 as described in Embodiment 1 such that the capacitor wasconnected with a diffusion layer in the transistor. The capacitor had astructure where a lower electrode made of TiN with a thickness of 30 nm,a dielectric film with a thickness of 10 nm and an upper electrode madeof TiN with a thickness of 30 nm were sequentially deposited.

The dielectric film was deposited by atomic layer deposition. Varyingthe deposition conditions as shown in Table 1, samples Nos. 1 to 8 wereprepared. Elemental compositions for the dielectric films thus preparedwere determined by SIMS (secondary ion mass spectrometry) The resultswere shown in Table 2.

Sample Nos. 2 to 4 had a composition represented by ZrO_(x)C_(y)N_(z),in which x, y and z met the conditions: 0.7<x, 0.1≦y≦1.25, 0.01≦z, andx+y+z=2.

On the other hand, sample Nos. 6 to 8 had a composition deviating fromthe range for x, y and z defined in the above formula. It may be foundthat although in all of sample Nos. 6 to 8 and Nos. 2 to 4,Zr(N(CH₃)(C₂H₅))₄ (tetrakis-methylethylamino-zirconium) is used, acomposition in a film obtained may vary depending on the depositionconditions. It demonstrates that a metal-compound film having acomposition represented by ZrO_(x)C_(y)N_(z) meeting the aboveconditions cannot be obtained simply by selecting a deposition gas asappropriate, but can be obtained only by appropriately selecting adeposition gas and optimizing the deposition conditions. The depositionconditions may include a deposition temperature, a deposition pressure,a deposition rate and a feeding time of a deposition gas. A combinationof these conditions may be optimized to obtain the above metal-compoundfilm.

Films prepared under the same conditions as those for sample Nos. 1 to 5were analyzed by a particle checker. In sample No. 1, contamination withparticles was observed in the film. In sample Nos. 2 to 5 and 6 to 8,contamination with particles was not observed.

Next, among the samples, sample Nos. 1, 3, 5 and 8 were determined for acapacity and a leak current for comparison. The results are shown inFIG. 14. In this figure, a plurality of measurement results are shownfor each sample because measurement was conducted in multiple runs,varying a film thickness deposited. The results indicate that sample No.3 has a smaller leak current than any other samples. Similar measurementwas conducted for sample Nos. 2 and 4, giving the results that they havea smaller leak current than sample No. 1, 5 or 8.

TABLE 1 NO. 1 NO. 2 NO. 3 NO. 4 NO. 5 NO. 6 NO. 7 NO. 8 Gas 1 ZrCl₄Zr(N(CH₃) Zr(N(CH₃) Zr(N(CH₃) Zr(OiPr)₄ Zr(N(CH₃) Zr(N(CH₃) Zr(N(CH₃)(C₂H₅))₄ (C₂H₅))₄ (C₂H₅))₄ (C₂H₅))₄ (C₂H₅))₄ (C₂H₅))₄ Gas 2 H₂O NO NO NOO₂ NO NO NO Gas 3 N₂ N₂ N₂ N₂ N₂ N₂ N₂ N₂ Gas flow ratio 1/2/3 1/2.5/101/100/1000 1/100/1000 1/100/1000 — 1/100/1000 1/20/1000 100/1/1000Deposition temperature (° C.)   200-400   200-400   200-400   200-400  200-400 150   200-400   200-400 Deposition pressure (torr) 0.05-100.05-10 0.05-10 0.05-10 0.05-10 0.05-10 0.05-10 0.05-10 Deposition rate(A/cycle) 0.4-3 0.4-3 0.4-3 0.4-3 10-50 0.4-3 0.4-3 0.4-3 Elemental O1.974 1.842 1.15 0.71 0.5 0.415 0.559 0.38 compo- C 0.02 0.105 0.8 1.191.499 1.583 1.34 1.61 sition N 0.001 0.053 0.05 0.1 0.001 0.002 0.0010.01 Cl 0.005 0 0 0 0 0 0 0

As described above, this invention can provide a highly reliablesemiconductor device having a high capacity comprising a film made of ahigh dielectric constant material containing Zr and/or Hf, in which aleak current is reduced in the film. When applying this invention to acapacitor, a capacitor having a high capacity with a reduced leakcurrent can be provided. Furthermore, when applying this invention to atransistor, a transistor in which a film thickness calculated as asilicon oxide film is smaller and which comprises a reliable gateinsulating film can be provided.

1. A process for manufacturing a semiconductor device, comprising the steps of: forming a ZrO_(x)C_(y)N_(z) (x+y+z=2, 0.7<x) film as a dielectric film on a lower electrode by atomic layer deposition using an oxidizer gas and a gas including Zr(N(CH₃)(C₂H₅))₄; and forming an upper electrode on said dielectric film; wherein when forming said dielectric film, a ratio of said gas including Zr(N(CH₃)(C₂H₅))₄ to said oxidizer gas is 1/100 or less.
 2. The process for manufacturing a semiconductor device as claimed in claim 1, wherein said oxidizer gas is a mixture of a nitriding gas and an oxidizing gas.
 3. The process for manufacturing a semiconductor device as claimed in claim 2, wherein said nitriding gas is NO and said oxidizing gas is NO₂.
 4. The process for manufacturing a semiconductor device as claimed in claim 2, wherein said nitriding gas is NO and said oxidizing gas is O₃.
 5. The process for manufacturing a semiconductor device as claimed in claim 1, wherein said oxidizer gas is O₃.
 6. The process for manufacturing a semiconductor device as claimed in claim 1, wherein said oxidizer gas is NO.
 7. The process for manufacturing a semiconductor device as claimed in claim 1, wherein said oxidizer gas is a mixture of NO and N₂, a ratio of NO/N₂ is 1/10,000 or more.
 8. The process for manufacturing a semiconductor device as claimed in claim 1, wherein when forming said dielectric film a nitrogen-containing gas is fed into a chamber.
 9. The process for manufacturing a semiconductor device as claimed in claim 8, wherein a cycle of said atomic layer deposition includes a step of feeding said nitrogen-containing gas.
 10. The process for manufacturing a semiconductor device as claimed in claim 1, wherein after forming said dielectric film, said dielectric film is nitrided by a plasma.
 11. The process for manufacturing a semiconductor device as claimed in claim 1, wherein said lower electrode and upper electrode films are formed of metal material.
 12. The process for manufacturing a semiconductor device as claimed in claim 11, wherein said metal material is TiN. 